When a dentist is attempting to determine whether an apparent anomaly in a patient's recent dental x-ray image merits further investigation and treatment, the dentist will often compare the recent x-ray image with one taken at a prior time. This is typically accomplished by placing both x-ray images within the dentist's field of view, perhaps on a single computer monitor, but as separate images. The dentist then alternates focus between the two images, in order to ascertain whether the apparent anomaly is new, has worsened over time, or else has remained fairly unchanged. If the apparent anomaly is new, or has worsened over time, the dentist may suspect the recent formation of a cavity or other damage to the patient's teeth.
Other medical professionals may perform a similar procedure using ultrasound images, magnetic resonance imaging (MRI) images, or other medical diagnostic images, to diagnose other medical conditions. The professionals use their own judgment, which can vary according to experience and other factors, to determine whether the amount of change is problematic, based on the time difference between when the different images were collected. Thus, current change analysis is subjective, and can potentially be inconsistent.
Unfortunately, there are multiple shortcomings with the above procedure: There is a possibility that a new anomaly in a diagnostic image may be missed by the medical professional, and also there is no objective score to quantify differences between the images. These problems can result in accusations of sub-standard care by medical malpractice attorneys if a patient later claims that a developing medical problem was not identified in the images.